:root{
  --percentag:100%;
}
.wrap{
  margin: 0;
  background-color: #000;
  height: 300vh;
}
.sticky{
  position: sticky;
  top: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  height: 100vh;
}

h1{
  font-family: helvetica;
  color: #FFF;
  margin: 0;
  padding: 0;
  font-size: 48px;
  letter-spacing: -0.3px;
  background-image: linear-gradient(75deg,
  rgba(255,255,255,1) 0%,
  rgba(255,255,255,1) 33.3%,
  rgba(255,255,255,0) 66.7%,
  rgba(255,255,255,0) 100% );
  // 背景颜色横向拉伸3倍
  background-size: 300% 100%;
  background-position-x: calc(100% - var(--percentag));

  background-clip: text;
  -webkit-background-clip: text;
  color: transparent;

  // transition: 2s background-position-x ease-in-out;
}

// h1:hover{
//   background-position-x: 0;
// }